According to Bonnie Ross, who was on stage at Gamescom, The Halo Channel is going to be our "home for Halo."
We were shown a demonstration featuring Halo: Nightfall (the live-action show shipping with Halo: The Master Chief Collection that fills the gap between Halo 4 and Halo 5: Guardians).
The channel will feature a mixture of gameplay, live action, discussion and more gameplay. A partnership with Twitch was also confirmed, where players will be able to share multiplayer action, speedruns, etc.
Players will be able to launch the Halo: The Master Chief Collection from the channel itself. We also got to see a tense multiplayer battle played on Sanctuary, which rounded off the Halo part of the show.